In some game machines which employ metal bodies as its media, a metal ball is moved within a specified space set for the game machine, and the receipt of a prize is determined in accordance with the movement of the ball. A typical example of such a game machine is, for example, a "pachinko" (Japanese upright pinball) game machine with which a game player causes a metal "pachinko" ball to move downward within a space between parallel planes provided with a large number of obstacles.
The "pachinko" game machine has a panel which defines the space for moving the "pachinko" ball, a glass plate which covers the panel at a fixed interval therefrom, and a projectile mechanism which project the "pachinko" ball to the upper part of the panel. The "pachinko" game machine is so installed that the panel extends in a substantially vertical direction. The panel is formed with a plurality of safe holes, each of which serves to make a hit when the "pachinko" ball has been led thereinto and driven out of the panel, and a single out hole into which the "pachinko" balls having failed to enter the safe holes are finally gathered to be driven out of the panel. A large number of pins (or nails) are placed on the panel protruding substantially perpendicularly thereto a distance corresponding to the diameter of each "pachinko" ball, so that the "pachinko" ball, as it falls along the panel may frequently collide with the pins thereby altering its moving direction. The pins are arranged on the panel in a predetermined distribution in which, while altering the moving direction of the colliding "pachinko" ball, they lead this ball to a safe hole in some cases and to miss a safe hole in other cases.
Owing to the construction as stated above, the "pachinko" game machines have individual characteristics, i.e., m some machines it is easy to register hits and in other machines it is difficult to register hits, depending upon the slight differences in the arrangement and inclinations of the pins. Even identical machines involve such differences as having safe holes with a high hit rate and safe holes with a low hit rate.
In a game center or the like wherein the game machines of this type are installed in large numbers, it is important to know the individual characteristics of the respective game machines as to management for profit administration and customer administration. If many of the machines register excessive hits the game center suffers a loss; whereas, if all the machines are difficult to register hits on, customers become disinterested, which is unfavorable to business. Accordingly, countermeasures need to be taken by knowing the individual characteristics of the respective game machines installed in the center.
For such a purpose, it is known to detect the moving courses of the "pachinko" balls in the "pachinko" game machine. In the official gazette of Japanese Patent Application Publication No. 3506/1989, for example, there is disclosed an apparatus equipped with an upper sheet and a lower sheet which have a pair of contacts. This technique senses the existence of the "pachinko" ball in such a way that the "pachinko" ball gets on the upper sheet and depresses it, whereby the pair of contacts touch.
With the prior-art apparatus, however, since the sheets have the pairs of contacts, they are restricted in arrangement, and they can be arranged only along the passages of the "pachinko" balls. It is therefore impossible to detect the motions of the balls from the point of view at which the whole panel is seen. The problem with this type of apparatus is that it is difficult to detect, for example, how the balls enter the safe holes and the out hole.
In addition, since the detection is based on the physical touching of the pair of contacts, sometimes the depression of the sheet becomes too weak to bring the pair of contacts into touch, so the motion of the ball is not detected. Besides, inferior touching can occur due to the wear, corrosion etc. of the pair of contacts. Further, the erroneous touching of the pair of contacts can occur by virtue of a vibration or the like or by chattering. For these reasons, the apparatus lacks reliability.
Another problem is that, since a pressure applied by the ball is utilized, the motion of the ball is delicately affected contrariwise.
Such problems can be encountered, not only in the "pachinko" game machine, but also in different machines. It is accordingly desired to overcome these problems.
On the other hand, when the sensor is arranged along the panel, there is a problem how to set a portion for detecting a metal body and a signal processing portion to drive the above-mentioned metal body detecting portion within the limited space without adverse effects, such as, for example, reducing a playing zone or obstructing a view or the like. This problem has not been considered heretofor.